Autofill textbox in screen painter
i create one custom infotype (PM01) , in that infotpe three textbox are maintained lets say A1, A2. A3
now i want , when user fill the A1 and A2 , A3 will automaticlly add the reuslt of A1 and A2 , bascially i need in textbox A3 = A1 + A2
please help me in this regards what event trigred once user leave the text box . so A3 should fill once user leave A2 or hit enter.